Machines for printing, cutting, creasing and otherwise processing flat carton blanks, including those used for flexographic printing, commonly include a plurality of interacting rolls such as print rolls, impression rolls, die rolls and anvil rolls. Some rolls, such as the print roll and the die roll must be axially adjusted in the initial set up of the machine, while other rolls such as the anvil roll must be constantly adjusted axially in order to reduce wear from the die roll. In the case of print and die rolls, the requirement is to initially set and thereafter maintain the rolls in precise axial alignment so that the printed images will be sharp and clear on each of the hundreds or thousands of blank cartons imprinted by the machine. In the case of the anvil rolls, the need is to be able to constantly adjust the axial position of the anvil roll of each cooperating pair so as to distribute the wear of the cutter dies along the axial length of the anvil roll.
This problem of axial alignment of such processing machine rolls is compounded by the fact that such rolls are many feet in axial length, frequently weigh thousands of pounds and must be driven through drive shafts and multiple gears by electric motors mounted outside the machine frame. In typical carton blank processing machines, the die roll may be driven directly by a first, main motor while the anvil roll is driven through a variable speed gear system comprising several gears, a register and a trim motor; all of such motors and gearing being positioned at the end of the roll shafts extending outboard of the machine frame. In addition, a hydraulic motor must be mounted on the opposite end of the anvil roll shaft in order to axially adjust the position of the anvil roll relative to the die roll.
While the foregoing multiple-motor and multiple-gear system is effective in driving the various rolls at the desired relative speeds, and in constantly adjusting the axial position of the anvil roll, it is apparent that these systems are complex, and the requirement for four or more gears introduces an undesirable amount of backlash between the gears. Such unavoidable backlash prevents maintaining such precise angular relationship between the cooperating rolls as is desired. Also, such multiple gears require a substantial amount of costly assembly time, and subsequent maintenance time, as well as making trouble-shooting and diagnostic efforts much more difficult. Even though each gear of the complex, multiple gear system is manufactured to extremely high tolerances, a certain amount of backlash and inaccuracy cannot be avoided. Therefore, there has long been a need for a simpler and more accurate motor-drive system for driving large carton blank processing rolls, while at the same time, providing for initial axial adjustment and continuous axial adjustment as briefly explained above.